Television – Image signal processing circuitry specific to television – Color television signal processing
Reexamination Certificate
1997-12-24
2001-09-18
Eisenzopf, Reinhard J. (Department: 2614)
Television
Image signal processing circuitry specific to television
Color television signal processing
C348S708000, C348S502000, C348S524000, C348S182000
Reexamination Certificate
active
06292231
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color signal generation circuit related to on-screen displays for a home-use VCRs or the like and, in particular, to a color signal generation circuit for coloring internally prepared displays.
2. Description of the Related Art
FIG. 1
shows a conventional color signal generation circuit for use in internally preparing display pictures. This circuit comprises a color signal generation circuit
4
, a divider
1
, and a shift circuit
2
. The color signal generation circuit
4
generates eight color signals having phases shifted in 45° steps. The divider
1
, comprising flip flops
1
a
,
1
b
, divides a 4fsc subcarrier whose frequency is four times that of a color burst signal (wherein 1 fsc is 3.58 MHz in NTSC), into a plurality of divided signals. The shift circuit
2
shifts the phases of divided signals outputted by the divider
1
, in accordance with a clock signal supplied via an inverter
3
.
As a result of the functions of the divider
1
and the shift circuit
2
, eight signals with various phases, namely &phgr;0 to &phgr;7 in
FIG. 2
, are generated. Six out of the eight generated signals are input into respective delay circuits
11
to
16
, which then delays received signals as required to adjust their phases so that they correspond to desired colors.
FIG. 2
shows waveforms of various signals.
According to a circuit as shown in
FIG. 1
, it is possible to generate a plurality of color signals because a 4fsc signal is divided into signals with phases shifted in 45° steps, and the resulting signals are delayed so as to correspond to desired colors.
The above color signal generation circuit, however, has a problem in that it requires a dedicated circuit for every color. As a delay circuit often requires a capacitor and cannot be easily integrated into an IC circuit, provision of dedicated circuits for all colors increases costs.
SUMMARY OF THE INVENTION
The present invention has been conceived to overcome the above problems and aims to generate a plurality of color signals by employing a reduced number of delay circuits.
The present invention also aims to generate a plurality of color signals by using a signal with a low frequency.
According to the present invention, a reference signal having a frequency four times as large as that of a color burst signal is divided into a plurality of divided signals each having a fsc frequency, phase shifted in 45° steps. One of the divided signals is output as a color burst signal in synchronism with a delayed reference signal. Thus, the phase of a color burst signal is delayed with respect to divided signals. The other divided signal has the phase which is relatively shifted from the phase of the color burst signal because the phase of color burst signal is shifted. Assuming that the phase of a color burst signal is shifted by 15° with respect to a reference signal, color signals for green, cyan, magenta, and red can be obtained from a plurality of divided signals.
Further, when another delay circuit is provided to delay a reference signal by a predetermined amount so that a divided signal is latched and output according to a delayed reference signal, further different color signals can be obtained. For instance, when a reference signal is delayed by 28°, using this delayed reference signal and a 180° signal, a yellow signal (180°−28°+15°=167°) is obtained. Similarly, using the delayed reference signal and a 360° signal, a blue signal (360°−28°+15°=347°) is obtained.
Likewise, when a 2fsc signal having twice the frequency of a color burst signal is used as a reference signal, and divided signals each having a fsc frequency and with phases shifted in 90° steps are obtained, various color signals can be generated with a smaller number of delay circuits. For instance, when one of the plurality of divided signals is output in accordance with a signal which has been delayed by 14° with respect to a reference signal and used as a color burst signal, some of the other divided signals can be used intact as color signals. In addition, other divided signals can also be used as color signals when they are adjusted to have different phases from those of the above by using a 27° or 43° delayed reference signal. As a result, a plurality of color signals are obtained.
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patent: 4303938 (1981-12-01), Berke et al.
patent: 4468687 (1984-08-01), Munezawa et al.
patent: 4578673 (1986-03-01), Yianilos et al.
patent: 5774184 (1998-06-01), Murakami
patent: 5786866 (1998-07-01), Sani et al.
patent: 5966184 (1999-10-01), Boehlke
Kawata Junichi
Naito Masayuki
Armstrong Westerman Hattori McLeland & Naughton LLP
Eisenzopf Reinhard J.
Natnael Paulos
Sanyo Electric Co,. Ltd.
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